Low-profile impeller bolt

ABSTRACT

An impeller for a self-primer pump is structured for attachment to the terminal end of a drive shaft by means of a bolt that is configured to provide a low profile such that the eye of the impeller is rendered capable of processing larger solids that are entrained in fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming priority to provisional patent application Ser. No. 60/707,088 filed Aug. 10, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to self-priming centrifugal pumps which are used to process fluids containing solids. Specifically, this invention relates to providing an impeller bolt that has a low profile to thereby accommodate processing of fluids with larger solids entrained in the fluid.

2. Description of Related Art

Self-priming centrifugal pumps are well-known and frequently used in industries where processing fluids with entrained solids is required. Self-primer pumps, also known as trash pumps, are characterized as having a casing which houses a suction chamber and a separation chamber divided by a wall or plenum. An impeller positioned in a volute section of the pump receives fluid from the suction chamber and delivers it by centrifugal action into the separation chamber where it is eventually expelled through an outlet.

Self-primer pumps are further characterized in the industry by the size of solids that can be processed by the pump. Self-primer, or trash, pumps are often rated by the size of solids that can be processed by the pump. Thus, a pump with a given diameter size of, for example, three inches may be rated as capable of processing solids up to two and one half inches in diameter while four to ten inch pumps may be rated as able to process solids up to three inches in diameter. However, it has been shown that the size or diameter of solids that are reported to be processable by a pump are actually not able to be processed. This is due in large part to the structure of the impeller, and principally to the bolt configuration at the eye of the impeller.

Prior art impellers in self-primer pumps are attached to the end of a drive shaft by means of a screw that is spaced from the impeller by a washer that is conically-shaped. Consequently, the head of the screw and the washer/spacer extend outwardly from the impeller and into the space between the vanes. As a result, larger sized solids can become trapped or lodged between the head of the screw and the wear plate that is positioned adjacent the impeller on the suction side of the pump. Solids lodged between the impeller and wear plate can cause the impeller to slow or stop in its rotation and/or can impede the flow of fluid through the pump, thereby leading to reduced pumping efficiency, or even pump failure.

Thus, it would be advantageous to provide an impeller design in a self-primer pump that enables the processing of larger solids so that pump efficiencies and operation are not compromised.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, the impeller of a self-primer pump is structured for attachment to the terminal end of a drive shaft by means of a bolt that is configured to provide a low profile such that the eye of the impeller is rendered capable of processing larger solids that are entrained in fluid. The bolt is also configured to eliminate the additional washer/spacer of prior art impellers, thereby reducing the cost of the pump and its repair or maintenance.

As previously noted, devices used in the prior art of centrifugal pumps to attach an impeller to the terminal end of a drive shaft typically comprise screws and washers that have a configuration which results in the screw and washer extending into the eye of the impeller. Such devices may be said to have a “high-profile” because they extend a distance into the eye of the impeller.

The present invention comprises a bolt for attaching the impeller to the terminal end of the drive shaft which is configured with a low-profile; that is, the bolt does not extend appreciably above the surface of the impeller and into the eye of the impeller. As a result, the impeller arrangement of the present invention allows the pump to process large-sized solids (e.g., three inches in diameter or larger) without having the solids become lodged between the impeller bolt and the wear plate.

The low-profile impeller bolt is generally formed with a unitarily formed shaft and head that eliminates the separate washer or spacer of prior art bolts. The head of the bolt of the present invention is substantially flattened in profile, thereby limiting the distance that the bolt extends into the eye of the impeller. As a result, larger solids that may be processed by the pump do not become lodged between the impeller and the wear plate of the pump.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:

FIG. 1 is an exploded view of a prior art impeller and drive shaft illustrating conventional means for attachment of the impeller to the drive shaft;

FIG. 2 is a view in cross section of a portion of a centrifugal pump of the prior art illustrating the positioning of the impeller to the pump inlet;

FIG. 3 is an exploded view of an impeller illustrating the low-profile impeller bolt of the present invention; and

FIG. 4 is a view in cross section of a portion of a centrifugal pump illustrating the low-profile impeller bolt of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A typical impeller arrangement of the prior art is shown in FIGS. 1 and 2 as a comparative illustration of the problem solved by the present invention. In FIG. 1, which illustrates an exploded view of an impeller 10, drive shaft 12 and means 14 for attaching the impeller 10 to the drive shaft 12, the means 14 for attachment comprises a standard socket head cap screw 18 and a washer 20. As seen in FIGS. 1 and 2, the screw 18 fits through the washer 20 and through the central opening 22 in the impeller 10 to threadingly engage the terminal end 24 of the drive shaft 12.

The washer 20 typically used in prior art impeller attachment is conically-shaped. As best illustrated in FIG. 2, when the washer 20 is secured in place by the screw 18, the washer 20 is positioned against the surface of the base or shroud 26 of the impeller 10. The washer 20 consequently provides a spacer 28 between the screw 18 and the shroud 26 of the impeller 10. So configured, the screw 18 and washer 20 of the prior art impeller 10 extend considerably away from the shroud 26 and into the eye 29 of the impeller 10. Larger sized solids 30 may then become trapped or lodged between the means for securing the impeller 14 and the wear plate 32, which is positioned adjacent the impeller 10, as depicted in FIG. 2.

In the impeller 40 of the present invention, shown in FIGS. 3 and 4, the means for securing the impeller 40 to the drive shaft 12 comprises a unitarily formed bolt 42 comprising a shaft portion 44 and a combined head and washer portion 46 having a low, or considerably flattened profile. The impeller 40 is formed with a central opening 48 through the back shroud 50 of the impeller 40 through which the shaft 44 of the bolt 42 is positioned to threadingly engage the terminal end 24 of the drive shaft 12.

As best seen in FIG. 4, the bolt 42 of the present invention presents a low-profile such that the head 46 of the bolt 42 does not extend appreciably above the surface of the impeller and into the eye 29 of the impeller 40. The distance that the bolt 42 of the present invention may extend above the surface of the impeller 40 may range from about one sixteenth of an inch to about one half inch. Consequently, the low-profile of the bolt 42 enables larger size solids 30 to enter into the eye 29 of the impeller 40 without becoming trapped or lodged between the impeller 40 and the wear plate 32. This results in improved pump operation.

In the embodiment of the impeller 40 shown in FIG. 4, the impeller 40 may be formed with a recessed land 52 surrounding the central opening 48 which is sized in diameter to accommodate the head 46 of the bolt 42 within the recessed land 52. The head 46 of the bolt 42 is thereby recessed into the surface of the shroud 50 lessening even more the potential impedance of the bolt 42 on solids 30 passing through the eye of the impeller 40. In such an embodiment, the bolt 42 may extend into the eye of the impeller 40 about, for example, one eighth of an inch. Alternatively, however, the impeller 50 may be formed without a recess such that the rear surface 56 of the head 46 of the bolt 42 is flush with the surface of the shroud 50, while still maintaining a low-profile.

The bolt 42 of the present invention may be structured with any suitable means for securing the bolt 42 in position against the impeller 40 as described, but is illustrated in FIGS. 3 and 4 as having a tool-receiving socket 54 for enabling securing and tightening of the bolt 42 to the drive shaft 12.

The low-profile impeller bolt of the present invention may be configured in a variety of ways to provide a low profile relative to the eye of the impeller. For example, the distance that the head of the bolt extends above the back shroud of the impeller may vary. Additionally, the circumferential shape or geometry of the head of the bolt may vary widely, especially if the head of the bolt is configured to be flush with the surface of the back shroud. Thus, reference herein to particular details or configurations of the low-profile impeller bolt of the present invention are by way of example, and not by way of limitation. 

1. An impeller for a self-priming pump, comprising: an impeller structured for processing solids-entrained fluid and having a shroud, at least one vane extending outwardly from said shroud and a central opening; a bolt insertable through said central opening of said impeller having a threaded shaft for connection to a drive shaft on which said impeller is positioned and a unitarily formed head and washer portion having tool-connection means for insertion and tightening of said bolt in the drive shaft, said unitarily formed head and washer portion having a low-profile.
 2. The impeller of claim 1 wherein said impeller is further structured with a recessed land surrounding said central opening and said unitarily formed head and washer of said bolt is sized in circumference to be received in said recessed land when secured to the drive shaft.
 3. The impeller of claim 1 wherein said bolt extends above said shroud a distance of from about one sixteenth of an inch to about one half inch. 